#include <iostream>
#include <cstring>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

// Father process -> read
// Child process -> write

int main()
{
    // 1.创建管道
    int fds[2] = {0};

    int n = pipe(fds);  // fds：输出型参数
    if(n != 0)
    {
        std::cerr << "pipe error" << std::endl;
        return 1;
    }


    // 2. 创建子进程
    pid_t id = ::fork();
    if(id < 0)
    {
        std::cerr << "fork error" << std::endl;
        return 2;
    }
    else if(id == 0)
    {
        // 子进程
        // 3. 关闭不需要的fd

        ::close(fds[0]);       // 关闭0端 读端

        int cnt = 0;
        while(true)
        {
            std::string message = "hello bit, hello ";
            message += std::to_string(::getpid());
            message += ", ";
            message += std::to_string(cnt);

            ::write(fds[1], message.c_str(), message.size());
            cnt++;
            ::sleep(1);
            break;
        }

        ::close(fds[1]);
        ::exit(0);
    }
    else 
    {
        // 父进程
        // 3. 关闭不需要的fd
        ::close(fds[1]);        // 关闭1端写端

        char buffer[1024];
        while(true)
        {
            ssize_t n = ::read(fds[0], buffer, 1024);
            if(n > 0)
            {
                buffer[n] = 0;
                std::cout << "child->father, message: " << buffer << std::endl;
            }
            else if(n == 0)
            {
                // 如果写端关闭
                // 读端读完管道内部的数据， 在读取的时候，
                // 就会读取到返回值0， 表示对端关闭， 也表示读到文件结尾
                std::cout << "n: " << n << std::endl;
                std::cout << "child quit ??? me too" << std::endl;
                break;
            }
        }

        ::close(fds[0]);
        pid_t rid = waitpid(id, nullptr, 0);
        std::cout << "father wait child success: " << rid << std::endl;
    }

    return 0;
}